1. Field of the Invention
The present invention relates to a battery state monitoring circuit capable of monitoring a state of a secondary battery and to a battery device provided with the secondary battery, a current controlling means, a battery state monitoring circuit, and the like.
2. Description of the Related Art
As shown in FIG. 2, a battery state monitoring circuit 20 is conventionally provided with battery voltage monitoring terminals 5 to 9, a charge control transistor gate connection terminal COP, a discharge control transistor gate connection terminal, and a control terminal 13 for a microcomputer 19. FIG. 4 shows a block diagram of a charge control circuit provided in the battery state monitoring circuit.
In a battery device 21, secondary batteries 1 to 4, a charge control transistor 14, a discharge control transistor 16, and a microcomputer 19 are connected with a battery state monitoring circuit 20 and external terminals, respectively. Either one of an external load 17 (for example, a CPU of a notebook personal computer etc.) that is operated by the supply of the electric power of the secondary batteries and a charger 18 for charging the secondary batteries 1 to 4 is connected between the external terminals of the battery device 21.
Now, when charging the secondary batteries with electricity, a charge completion signal is outputted from an IC upon charging fully the secondary batteries with electricity to stop the charging operation. At this time, a hysteresis voltage signal is outputted together with the charge completion signal. The hysteresis voltage in this case is provided in order to prevent the battery voltage from being reduced to carry out the recharge upon stopping the charging operation. If the level of the charge voltage becomes below a hysteresis voltage area, then the charge completion state is canceled, which makes it possible to recharge the secondary batteries with electricity (refer to FIG. 5).
On the other hand, when the charging operation is inhibited due to a high temperature or the like, a charge inhibition signal is outputted from the microcomputer irrespective of the charge completion signal. At this time, the hysteresis voltage signal is outputted together with the charge inhibition signal to stop the charging operation (refer to FIG. 6).
With conventional battery state monitoring circuit and battery apparatus, after generation/cancel of the charge inhibition signal from a microcomputer due to a high temperature or the like as shown in FIG. 6, it is impossible to recharge the secondary batteries with electricity. There is, as a result, encountered the problem that it is impossible to recharge the secondary batteries as long as the level of the discharge voltage becomes lower than that of the hysteresis voltage. Impossibility of the recharging operation means that the level of the battery voltage at the time concerned is lower than that of the battery voltage when the charging operation is completed, which results in that a time period of use of the secondary batteries at the time concerned becomes shorter than that when the secondary batteries are fully charged. In addition, there is encountered the problem that since the cycle of the charging operation is shortened, the batteries are quickly degraded.
In the light of the foregoing, the present invention has been made in order to solve the above-mentioned problems associated with the prior art, and it is, therefore, an object of the invention to provide a battery apparatus having a long duration (use time period).
In order to attain the above-mentioned object, the present invention may provide a battery state monitoring circuit in which the condition of xe2x80x9ca hysteresis voltage is generated only when outputting a charge completion signal from an ICxe2x80x9d is imposed on an output of a hysteresis voltage signal, and hence the hysteresis voltage signal can not be generated on the basis of only a charge inhibition signal outputted from a microcomputer.